The Gordon Conference on Second Messengers and Protein Phosphorylation in June 1991 will concentrate on the structure and function of proteins involved in signal transduction pathways, interaction between components of these cascades, and the mechanisms of modulation of their function. Considerable progress has been made in the identification of proteins involved in signal transduction. The current efforts in many laboratories is to examine the specificity of interactions among the components in the pathway. The design of the conference will bring out the multifaceted approaches currently being used to examine these questions. These approaches include the genetic analysis of pathways in simpler organisms, identification of the mutations in G proteins underlying human disease, and the biochemical studies of protein interactions. The Conference should provide a lively form for the exchange of information, ideas and prospects for future work. Last year approximately 80% of the participants in the conference presented data either in posters or as speakers. Such active participation by the conferees at all levels, including graduate students, postdoctoral fellows as well as junior and senior investigators, encourages discussion and fosters new interactions. The sessions planned for the 1991 Conference are: 1) Signalling Pathways in microorganisms focussing primarily on yeast and Dictyostelium discoideum 2) Role of small GTP binding proteins in regulation of cellular function 3) G protein structure and function 4) Mechanisms of sensory transduction in the visual and olfactory systems 5) Regulation of gene expression 6) Receptor/G protein Interactions 7) The structure and function of enzymes which generate second messengers 8) The mechanisms of bacterial chemotaxis 9) Genetic analyses and the elucidation of G protein function.